U.S. Pat. No. 5,675,487 A discloses a system for controlling solar radiation through a window. The control system comprises fenestration blinds that are disposed at the window and that are adjustable in angle to control solar radiation entering the window. First and second photovoltaic sensors are disposed proximate respective exterior and interior sides of the fenestration blinds for providing a signal representative of the incident solar radiation at the respective exterior and interior sides. An electrical motor is disposed proximate the window and is operably connected to the fenestration blinds in a manner to control the angle thereof. A microprocessor control device is provided for providing control signals to the motor to adjust the angle of the fenestration blinds. In one mode of operation, the microprocessor compares the ratio of the signals representative of solar radiation incident at the exterior and interior sides in response to adjustment of the angle and a preset ratio stored in the microprocessor representative of minimum direct light and maximum indirect light entering the window and continues to provide control signals to the motor to adjust the angle until the ratio of the signals approximates a preset ratio. The control system has the disadvantage that the continuous adjustments of the fenestration blinds may disturb the users and may therefore not be appreciated by them.